Fixes After BP Spill Not Enough, Board Says

The 2010 disaster at BP’s Deepwater Horizon killed 11 workers and dumped millions of gallons of oil into the Gulf of Mexico.CreditCreditGerald Herbert/Associated Press

HOUSTON — Federal safety regulators warned on Thursday that another disastrous offshore oil well blowout could happen despite regulatory improvements in the four years since a BP well explosion in the Gulf of Mexico killed 11 workers and dumped millions of gallons of oil into the sea.

The warning came with the release of a report by the Chemical Safety Board that placed much of the blame for the destruction of the Deepwater Horizon, the rig involved in the BP disaster, on a buckled steel drill pipe that interfered with the functioning of an emergency device in sealing the well.

The report was consistent with several other government reports on the accident, which pointed to multiple causes for the disaster. But the new report focused more acutely on the malfunction of the so-called blowout preventer, the rig’s last defense, which was supposed to cut through the drill pipe and seal the Macondo well.

Unlike previous reports, the Chemical Safety Board study concluded that the blowout preventer’s blind shear ram, an emergency hydraulic device with two cutting blades, probably activated as intended on the night of the accident.

But the shear ram did not seal the well drill pipe; instead, it punctured the pipe and sent oil and gas gushing to the surface. The study found that the drill pipe had buckled under the tremendous pressure of the oil and gas rising from the well from the initial blowout, while previous studies concluded that the pipe buckled days after the initial explosion.

Perhaps most notable in the report was the warning that the problems revealed in the episode could cause future accidents — although the principal government regulatory agency monitoring offshore drilling has been thoroughly revamped and the oil and gas industry has become more alert.

“Although there have been regulatory improvements since the accident, the effective management of safety-critical elements has yet to be established,” Cheryl MacKenzie, the board official who led the investigative team, said in a statement. “This results in potential safety gaps in U.S. offshore operations and leaves open the possibility of another similar catastrophic accident.”

The report found several problems with the blowout preventer, which was built by Cameron International and maintained by Transocean, the owner of the Deepwater Horizon. It said the component that was meant to shear and seal the well was not suitable for the drilling operation and could not reliably be counted on to shear the drill pipe. It noted two instances of imperfect wiring, along with two backup battery failures affecting the electronic and hydraulic controls for the blowout preventer’s blind shear ram, although the shear instrument was able to operate anyway.

The board concluded that neither Transocean nor BP had performed adequate regular inspections or testing of the blowout preventer’s emergency systems. As a result, the report said, the systems responsible for shearing the drill pipe in emergency situations were “compromised” before they could be deployed.

Geoff Morrell, a BP senior vice president, said in a statement that the core findings of the report were consistent with previous reports in concluding that there were multiple causes to the accident. That is an argument BP has made in a court in New Orleans as a federal judge decides how much money BP and other companies must pay in environmental penalties.

But Mr. Morrell added that some new Chemical Safety Board conclusions were “based on flawed assumptions,” including the theory that the blowout preventer “could not cut the drill pipe because the pipe had buckled before the explosion on the rig due to pressure differentials.”

A Transocean spokesman, Chris Kettmann, said his company concurred with the board’s conclusion that the buckled drill pipe prevented the blind shear ram from properly functioning. But he added, “We respectfully disagree with other findings in the report, including and especially C.S.B.’s assertions regarding Transocean’s operational and safety culture.”

The board also came to broader conclusions covering the whole offshore industry.

“Drilling continues to extend to new depths, and operations in increasingly challenging environments, such as the Arctic, are being planned,” the board chairman, Rafael Moure-Eraso, noted in a statement. “To maintain a leadership position, the U.S. should adopt rigorous management methods that go beyond current industry best practices.”

A version of this article appears in print on , Section B, Page 2 of the New York edition with the headline: Fixes After BP Spill Not Enough, Board Says. Order Reprints | Today’s Paper | Subscribe